PhD defence: Drivers and implications of circulation and evaporite deposition patterns

During the early Messinian, ca 7.2 Million years ago, the Mediterranean Sea already resembled the one we know today. However, towards the end of the Messinian its pleasant oceanic waters turned into a brine, leading to massive gypsum and halite deposits which lowered the global ocean salinity significantly. This event, called the Messinian Salinity Crisis, occurred in a geologically short time span of ca 600 kyr between 5.97 Ma and 5.33 Ma. 

With various physics-based model approaches and mass balance calculations we explored the feasibility of different theories and interpreted their implications with an interdisciplinary lens. 

We conclude that the reduction of the water exchange between Mediterranean Sea and Atlantic was not continuous and already started before 7.2 Ma. Based on the analysis of a similar model we assume that there was only brief period during which gypsum was deposited in the margins of the western mediterranean, while halite was accumulating in its depth. Deposits in the depression between Mallorca and Ibiza further indicate that gypsum formation was not limited to shallow marginal basins and that a sea level drop disconnected the basin during halite precipitation, which leads to implications regarding the progression of salinity that would explain more than 90% of the halite volume found in both western and eastern basin. 

Our conclusions highlight that it is important to look at changes over time instead of snapshots focusing on a moment in time, as the Mediterranean Sea was in a continuous state of transition.